engine miss

[Shimy87]

Adjusted fp to 43 lbs, hose off, it was at 49. Also unplugged computer over night. Now my crusing blms are 125-128 so thats better from 118. Still has the miss and now also has a slight stumble from off idle like leaving a stop light. Lowering the fp got the computer to stop pulling fuel at cruise I think?? Any ideas? Don't think I should crank up fp beyond 49 with hose off?

[Steve Wood]

warm it up and check the compression.  give it the same number of "bumps" on each cylinder and see if they all resemble one another

[Shimy87]

Each got 7 bumps and every cylinder was right at 150 on my old casper gauge. Going to put some new ngk UR5 plugs in tomorrow to remove that potential issue. Then run it with fp gauge hooked up to see if maybe the pump is going??

The O2s jump all over but do seem to show lower low numbers than my car does, don't know what if anything that is telling me?

It runs very smooth when on the gas or up to highway speed but at that 40 mph very low throttle it has that noticeable miss

[Steve Wood]

Does not sound like a pump problem.  Still sounds like it is going lean at that point

[Steve Wood]

Do all my usual suggestions

Be sure the intake bolts are all about the usual tightness.  Spray carb cleaner around throttle body/plenum joint. 
Around the vacuum block and around the base of the plenum.  Be sure the joints between the maf and the turbo are not leaking.  Pinch off the pcv line.  Make sure none of the metal vacuum lines are cracked and check valves are good...    make sure there is no small leak under the egr valve base. Spray around the IAC to make sure it is not cracked or leaking

It sounds like it is pulling too much air from some place as the throttle is cracked... 

[Steve Wood]

MIght also try setting the Translator one step rich on the idle.

[Shimy87]

Checked and zero leaks anywhere. Tps was a bit low at ,38 so corrected that. No time to test drive but will tonight. On the tps ....I can't get WOT to get above 4.35. Not causing this issue but its low

[Steve Wood]

That is not low at all.  It does not matter if it is set there or 4.8.  It does not use tps other than for normal cruising.  .38 is also in the window of adjustment.  Factory says .35 to .45v as I recall.  If the car is running and you move the tps, you will get a change in idle but when you turn it off and restart it, the idle returns to where the chip is telling it to idle.

I am sure you sprayed around the injector bases so my next suggestion is to go to one step richer on the maf

[Steve Wood]

did you put a new Denso O2 sensor in it?

[Shimy87]

No, but they are only $15 so I will put one in

[Steve Wood]

If no leaks,then o2 or maf sensor calibration would seem likely

[Shimy87]

Hope its tha O2 sensor, just tested car and it still does it. Tried maf setting at standard and at 10 % rich at idle....the miss feels the same in both but the readings are lower in standard setting.

[Steve Wood]

I'm really lost.  It seems like it is getting too much air and leaning out which can cause the problem you describe.  You might try switching mafs between the two cars if the O2 sensor does not fix it...

[Shimy87]

Been wracking my brain on this one and I agree it time to start swapping known good parts and see if I can correct this. As usual your right and its got to be a fuel delivery issue. If it was a miss caused by an ignition problem I would think O2's would go up as it wouldnt be burning the fuel correctly?? I'm going to check for a leak again but last time I had so much carb cleaner sprayed everywhere I was waiting for it to burst into flames..haha.

[Steve Wood]

I think the o2s go down when the fuel does not burn correctly so the net result is a lean cylinder.  I may be "misrembering" tho LOL

In other words, the O2 sensor measures the oxygen left in the cylinder after combustion but it does not measure normal air...think that is what Bob Bailey explained to me... 

I used to say that three was the ideal number of buicks to own for optimum swapping...

Now, I am confused and don't know...

Can you feel it miss when the car is in Park and you crack the throttle?  If so,  disconnect one injector at a time and see if the problem gets worse after each one is disconnected, or do you find one that stays the same?